Are employees required to disclose purchases and sales of their own companies stocks? If yes, are these disclosures publicly available? If yes, where?
Where do companies such as INK Research get their "insider" data?
Have a look at Decoding Inside Information. From Section II (Data):
The data in this study are collected from several sources. Our primary data on insider trades are drawn from the Thomson Reuters insider filings database. Section 16a of the Securities and Exchange Act of 1934 requires that open-market trades by corporate insiders be reported to the Securities and Exchange Commission (SEC) within 10 days after the end of month in which they took place. This 10-day deadline was later changed to a 2-day deadline in 2002. The median delay between trade date and report date over our entire 22 year sample is 3 days.
The whole paper is very interesing. From the intro:
In this paper we provide a new framework for thinking about detection and information flow in the capital markets. Using a simple, novel approach, we decode whether there is likely to be information in a given insider’s trades. In doing so, we show that there is predictable, identifiable “routine” insider trading that is not informative for the future of firms.